The field of the invention is cleaning apparatus for cleaning carriers used to hold and transport semiconductor wafers and similar flat articles requiring low contamination levels.
The processing of semiconductor wafers, substrates, photomasks, flat panel displays, data disks, optical and MEMS media and other flat articles (collectively referred to here as “wafers”) is very sensitive to contamination. These articles require extremely low contamination levels. Even microscopic contaminants can cause defects. Accordingly, it is necessary to maintain a high level of cleanliness during virtually all stages of manufacture.
Wafers are typically processed in batches. Batch handling may occur throughout the entire production process, or for one or more processing steps or related handling operations. Batch processing usually uses a carrier to hold the wafers. The wafer carriers can be of various designs and are generally a protective case or box optionally including a removable door. These carriers or boxes are known as FOUPs, FOSBYs or cassettes. In these types of carriers, the wafers are held and enclosed, to protect them from contamination during movement and storage within the processing facility. After each use, the wafer carriers must generally be cleaned to avoid having particles and contaminants on the carriers contaminate the wafers. Cleaning the boxes, however, can be difficult because they typically have features such as slots, grooves, and/or apertures.
Carriers have been successfully cleaned in centrifugal cleaners. See, for example, U.S. Pat. No. 5,738,128 incorporated herein by reference. In these centrifugal cleaners, the box is loaded onto a rotor, with the open front side of the box facing radially outwardly from the rotor. The box is then sprayed with cleaning fluids, and then with drying gases, while the rotor turns. Centrifugal force helps to remove cleaning fluids from the box, to help dry it. While these techniques have worked well for different types of boxes, disadvantages remain in loading, holding and unloading especially larger size carriers.
Another engineering challenge is that carrier doors in current systems are generally cleaned separately from the boxes themselves. Accordingly, matching the doors back with their respective boxes after cleaning is often difficult, error prone, and time consuming. Thus, there is a need for a system that efficiently cleans carriers, as well as a system that cleans carriers and carrier doors together.